As computing devices are made smaller with more wiring connections, IC (Integrated Circuit) die packages are developed that include more than one die in a single package. Since the die is normally much smaller than a package, the additional dies do not significantly increase the size of the package. Accordingly by combining multiple dies in a single package, fewer packages are required for the device allowing the device to be smaller and reducing the distance between the dies. The long connection path between two dies in different packages may reduce the speed of the data communications between the dies. These longer connections have more reactance and more impedance and are more susceptible to noise and interference. All of these characteristics restrict the amount of data that can be carried through the data over a particular time interval.
The dies inside a package can be connected by stacking the dies and attaching the front side of one die to the back side of the other die. Vias through the back side of the die allow for the dies to connect directly. The dies inside a package can also be connected using an interposer. There are a variety of different interposer configurations but in most of these the dies are attached to the interposer and the interposer is used to carry signals between the dies and perhaps also to a package substrate.